Generally, the electronic document communication has been restrictively performed only in a specific industrial group or community based on an individual unique regulation of corporations/institutions.
Further, there are problems in that an email is used as an assistant means between general individuals or between an individual and an enterprise/institution without considering a concept of a reliable electronic communication, or online communication is performed only when the individual, an individual business, or a small company access to an web site of the enterprise.
Therefore, it is expected that not only the enterprise that can possess a predetermined size of communication system, but also the individuals, the individual business, or the small company may build an electronic document communication based infra that guarantees the reliability of the communication.